Geology and hydrocarbon potential of the Taylorsville Basin, Virginia and Maryland

The Taylorsville basin is a rift basin of Late Triassic to Early Jurassic age in east-central Virginia and adjacent Maryland. The basin has been a target for oil and gas exploration by Texaco and partners in the 1980s, when six continuous cores were drilled followed by three deeper exploratory wells. Currently, no hydrocarbon production has been established from the basin. Relatively thick sequences of dark-colored shale that may serve both as source rocks and self-sourced reservoirs for hydrocarbons have been encountered near the basin's center. The current USGS assessment concludes that the mean values for undiscovered hydrocarbons in the basin are 1,064 billion cubic feet of gas (BCFG) and 37 million barrels of natural gas liquids (MMBNGL). The Taylorsville basin contains one composite total petroleum system, in which the hydrocarbon potential of the source beds and potential reservoirs were combined and assessed together as a single continuous gas assessment unit. Potential source rocks within the Taylorsville basin include coals and shales of the Triassic Falling Creek and Port Royal formations. Vitrinite reflectance data indicate that the source rocks range from pre-peak oil to peak gas thermal maturity. Potential reservoir rocks are continuous accumulations in shales, coal beds, and tight sandstones as well as possible conventional accumulations in porous and permeable strata within the Triassic Dowell and King George groups. However, well log based sandstone porosity values are generally low. Potential seals may be present in shale beds or igneous intrusions within the basin or by pore-throat restrictions within the continuous reservoir bodies.